Low profile truck tow conveyor system

ABSTRACT

A floor level conveyor system is provided with a chain sliding in a low profile guideway which engages a tow pin mounted on a truck to propel the truck. The chain is of the rivetless type having its chain pins vertical. Its upper link extends beyond the chain pins on each end partly over the center links and is substantially smooth and continuous for the tow pin to ride over until it reaches a pusher assembly. The upper link has two Tshaped recesses to receive T-shaped upper head of the chain pins and abutment surfaces on its ends to prevent over-riding of adjacent upper links. The lower links have a wearing surface projecting below the lower ends of the chain pins to support the chain. The chain operates around horizontal curves, and vertical curves of a larger radius, without losing the continuity of the upper links.

United States Patent Galloway et al.

[451 May 16, 1972 [54] LOW PROFILE TRUCK TOW CONVEYOR SYSTEM [72] Inventors: Roderick S. Galloway, Atlanta, Ga.; Horace M. Swartz, Doylestown; Joseph H. Walsh, Chalfont, both of Pa.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: May 5, 1970 21 Appl. No.: 34,673

2,685,361 8/1954 Garman et al. ..198/181 Primary Examiner-Arthur L. La Point Assistant Examiner-Robert Saifer Attorney-F. W. Anderson and C. E. Tripp [57] ABSTRACT A floor level conveyor system is provided with a chain sliding in a low profile guideway which engages a tow pin mounted on a truck to propel the truck. The chain is of the rivetless type having its chain pins vertical. lts upper link extends beyond the chain pins on each end partly over the center links and is substantially smooth and continuous for the tow pin to ride over until it reaches a pusher assembly. The upper link has two T-shaped recesses to receive T-shaped upper head of the chain pins and abutment surfaces on its ends to prevent overriding of adjacent upper links. The lower links have a wearing surface projecting below the lower ends of the chain pins to support the chain. The chain operates around horizontal curves, and vertical curves of a larger radius, without losing the continuity of the upper links.

24 Claims, 29 Drawing Figures P'Atrminnmsm 3.662.690

SHEET 1 BF 6 F/Gl.

INVEN TORS RODERICK SGA LLOWAY HOPACE M. SWARTZ JOSEPH H. WALSH Byj Jfl/MM ATTY'S SHEET 2 OF 6 PATENTEUHM 1s m MEN INVEN TORS RODERICK SGALLOWAY HOF ACE M SWAFPTZ JOSEPH. H. WALSH '86. A 7 7 Y S P'A'TENTEDMY 1s m SHEET u UF 6 Fl 6. l2.

' FIGJT IN VE/V TOPS RODERICK SGALLOWAY HORACE M SWAHTZ JOSEPH H. WALSH LOW PROFILE TRUCK TOW CONVEYOR SYSTEM BACKGROUND OF THE lNVENTlON 1. Field of the Invention This invention relates generally to an under-the-floor type truck tow conveyor system and more particularly to a conveyor having a low cross-sectional profile adapting it to fit into a shallow trench below the floor line or to extend only a nominal distance above the normal floor line of a warehouse, shipping terminal, or factory building. The invention includes a novel rivetless type sliding chain, having smooth, substantially continuous top surface with ends which extend partly over the adjacent center links and vertical connecting pins. The chain slides in an enclosed guideway, having an upper slot through which a vertically depending tow pin on the truck operates. The lower end of the tow pin slides along the smooth top surface of the chain until it drops into a pusher dog assembly where it is held so that the chain can push the tow pin and truck.

2. Description of the Prior Art A typical low profile floor conveyor is disclosed in US. Pat. No. 3,265,013 issued to A. Czamecki on Aug. 9, 1966. The conveyor there disclosed consists of a chain made up of horizontal flat bars vertically off-set at one of its ends in an overlapping relationship with the adjacent links. The chain is guided in its track by a horizontal roller mounted on a vertical pin through the ends of these links, permitting horizontal articulation of the chain. At the opposite ends of the links additional vertical bars are provided and the links are joined with a horizontal pin, permitting vertical articulation of the chain. This horizontal pin is extended to carry two rollers which in turn support the chain in a rolling manner. A pusher dog assembly is also provided which has angled cam surfaces to direct the truck tow pin sideways into a branch path.

A flush top slider chain for floor conveyors is disclosed in US. Pat. No. 2,689,036 issued to Mullen et al on Sept. 14, 1954. This conveyor chain comprises an upper link with a relatively wide top plate which slides on top of the channel track flanges and covers the otherwise open slot between the track channels. This top plate has semi-circular ends and has pockets so the chain pin heads are flush with the top plate surface. A lower link of conventional rivetless chain type is parallel to but vertically spaced apart from the upper link. A special open center link similar to the conventional rivetless chain center link is used between the upper and lower links but in overlapping end-to-end relationship. This center link has a raised central portion to which a separate narrow cross bridging plate is attached having two arcuate recesses conforming generally to the ends of the adjacent upper links and generally maintaining their flush top surface. The links are connected by a conventional vertical chain pin with an upper head having two projections 180 apart and at intervals a counterweighted pivoted pusher dog is mounted on top of one of the upper links for engaging a tow pin on a vehicle and thereby causing it to move with the chain. The US. Pat. No. 2,685,361 granted to L. H. Garman et al on Aug. 3, 1954 also shows a floor type conveyor chain having a flush type top link similar to the Mullen et al patent but using a flat bar type of chain in lieu of the rivetless chain.

Another form of rivetless chain with a substantially closed upper surface is disclosed in US. Pat. No. 2,696,742 to S. W. Otto et al. issued on Dec. 14, l954. In this chain its connecting pin, coupling adjacent links, is horizontal and has special flush type heads so arranged as to be self-locking in their operating position. The two vertical outer sidebar links are horizontally spaced apart to provide space for the center link, but are joined by another bridging member in their central portion which is flush with the top surface of the sidebar links.

Other forms of prior art generally show chains having their connecting pins horizontal and various means of providing bridging members between the outer links and cam surfaces on the center links so that a substantially closed and continuous top surface is presented for the bottom of the tow pins to ride over without becoming jammed except at the specific pusher area. Many of these chains are also supported by rollers.

In earlier forms of truck tow conveyors a conventional rivetless chain was suspended from anti-friction roller idlers and tow pin pushers operating in a double rolled channel track. This track and the clearance below for the chain required a total depth of 6% to 10% inches and a minimum width of 6 inches; whereas the newer low profile conveyor requires a depth of approximately 3% inches and a width of 2 inches.

SUMMARY OF THE INVENTION In a truck tow system a truck or other vehicle is pushed along a floor or similar surface by the engagement of a movable vertical pin mounted on-the forward end of the truck with a pusher in an endless chain mounted in a chain guideway just below the floor. The guideway is generally U-shaped and has a narrow continuous opening or slot at its top at the floor level for receiving the tow pin and guiding it throughout the path of the conveyor. A drive is connected to the chain to cause it to move.

Since the tow pin is normally just dropped into the open slot of the guideway at any point and the chain itself is not completely visible, it is very desirable to have the top surface of this chain relatively smooth and continuous so the tow pin can slide over the top until it reaches a pusher assembly connected in the endless chain. The pusher assembly traps the tow pin and then pushes the tow pin and the truck as the chain moves. A forged steel rivetless type of chain is one of the most economical and strongest chains for its weight so its use is highly desirable in this service. Because of the shallow depth of this low profile conveyor it is desirable to have a chain that is as compact vertically as possible and a design suitable for sliding on the bottom of the guideway meets this requirement.

This invention particularly relates to a low profile conveyor system in which a shallow guideway and a new sliding type rivetless chain, having a substantially smooth and continuous top surface suitable for operation in this guideway, is provided. The chain has a relatively long, specially contoured, horizontal upper link extending partially over the area of the adjacent center link to provide a substantially smooth and continuous surface for the tow pin even when articulating around horizontal and vertical curves and to prevent adjacent upper links from telescoping, one under the other on vertical curves. A lower link is provided with a special wearing shoe of relatively large area projecting below the heads of the chain pins for sliding contact with the bottom of the chain guideway. A conventional open center link is spaced vertically between the upper and lower links in an overlapping end-to-end relationship. A new type of chain pin having a T-shaped upper head and an I-shaped lower head connects the upper, lower and center links. The upper head of this pin normally fills a mating pocket in the upper link and the aperture therethrough required for the removal of the lower head of the pin through the upper link on dis-assembly and maintains the continuity of the top surface of the upper link. A pusher assembly, comprising a conventional open center link and a combination pusher dog and wearing shoe unit, is connected in the chain at spaced intervals to provide the pushing surface of the chain for the tow pin. The vertical chain pin and upper link arrangement permits relatively sharp horizontal turns without the necessity for increasing the width of the chain guideway on the turns except as required on the inside radius of the turn for the use of anti-friction rollers. A curved shape on the ends of the center link provides limited vertical articulation so as to give multiplane operation of this chain. I

Accordingly it is an object of this invention to provide an improved low profile truck tow conveyor system.

Another object is to provide a conveyor system with a rivetless'type chain having a substantially smooth and continuous top surface for operating in a relatively shallow and narrow chain guideway.

Another object is to provide a chain which will negotiate both horizontal and vertical curves in a low profile conveyor system while maintaining a substantially smooth and continuous upper surface of the chain for the truck tow pin to ride upon until engaged with a pusher assembly.

A'further object is to provide a chain operating with its chain pins vertical and its chain links horizontal which will have relatively few parts and give long trouble free operating life while sliding on the bottom of the chain guideway.

The manner in which these and other objectives of the invention may be obtained will be apparent from the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational view of a truck tow system, using the conveyor of the present invention and showing the chain guideway partially cut away.

FIG. 2 is an enlarged cross-sectional view of the conveyor at a pusher assembly taken along line 2-2 in FIG. 1.

FIG. 3 is an enlarged cross-sectional view of the conveyor at a link pair taken along line 3-3 in FIG. 1.

FIG. 4 is a plan view of the conveyor chain removed from its guideways and showing the different links and a pusher.

FIG. 5 is an elevational view of the conveyor chain shown in FIG. 4.

FIG. 6 is a schematic plan view of a horizontal roller turn in the conveyor with parts broken away.

FIG. 7 is an enlarged cross-sectional view of the roller turn taken along line 7-7 in FIG. 6.

FIG. 8 is a schematic elevational view of a portion of a vertical curve in the conveyor.

FIG. 9 is a plan view of an upper link of the conveyor chain.

FIG. 10 is a side elevational view of the upper link shown in FIG. 9.

FIG. 11 is a plan view of a lower link of the conveyor chain.

FIG. 12 is a side elevational view of the lower link shown in FIG. 11 partly broken away.

FIG. 13 is a cross-sectional view of the lower link taken along line 13-13 of FIG. 11.

FIG. 14 is a plan view of a pusher assembly of the conveyor chain;

FIG. 15 is aside elevational view of the pusher assembly shown in FIG. 14 partly broken away.

FIG. 16 is a cross-sectional view of the pusher assembly taken along line 16-16 of FIG. 14.

FIG. 17 is a plan view of a second embodiment of a pusher assembly utilizing an upper link.

FIG. 18 is a side elevational view of the pusher assembly shown in FIG. 17.

FIG. 19 is a side elevational view of a chain pin.

FIG. 20 is an end elevational view of the chain pin shown in FIG. 19.

FIG. 21 is a plan view of the chain pin shown in FIG. 19, showing the upper head.

FIG. 22 is a cross-sectional sectional view of the chain pin taken along line 22-22 of FIG. 20, showing the bottom head.

FIG. 23 is an end elevational view of a second embodiment of a chain pin.

FIG. 24 is a side'elevational view of the chain pin shown in FIG. 23.

FIG. 25 is a top view of the chain pin shown in FIG. 23.

FIG. 26 is a plan view of a second embodiment of a lower link.

FIG. 27 is a sectional side view taken along line 27-27 of FIG. 26.

FIG. 28 is a cross-sectional view taken along line 28-28 of FIG. 26.

FIG. 29 is a perspective view of the removable wearing shoe of the lower link shown in FIG. 26.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A truck tow conveyor system is generally indicated in FIG. 1 where a wheeled truck 35 rolls on a given surface, such as a floor 36. A vertically movable tow pin 37 is mounted on the front of the truck 35. Pin 37 in its operating position projects below the level of floor 36 through an open slot 38 (FIG. 2) in a chain guideway 39. An endless chain 40 slides in the bottom of the guideway. Upon being lowered into the slot, the tow pin 37 rides over the upper surface of chain 41 until it reaches a pusher link 42 where it drops into engagement with a pushing face 43. The chain then pushes the tow pin 37 and the truck 35 as it moves.

The cross section of the chain guideway 39, as shown in FIGS. 2 and 3, comprises a U-shaped bent plate having a narrow horizontal bottom portion 45 and two vertical flanges 46. A narrowbar 47 is welded to each vertical flange 46 so that the top edge of bar 47 is approximately flush with the top edge of flange 46. The open space between the bars 47 defines the tow pin guiding slot 38. A wear plate 48 is welded to the inner surface of the bottom portion 45 of the guideway 39 to provide an additional wearing surface for the chain to slide upon. The chain guideway 39 may be made up of convenient lengths of straight track sections, vertical curves and transitional sections between the straight sections and either the vertical curves or a horizontal roller turn.

When a horizontal curve is in the path of the conveyor, a roller turn 50 is used as shown in FIG. 6. Antifriction rollers 51 are mounted at spaced intervals on the inner radius of the turn. The cross section is generally similar to the straight section as shown in FIG. 2 but is wider to allow room for the roller 51 as shown in FIG. 7. A roller turn guideway consists of a bottom plate 52, a wear plate 53, two vertical plates 54 and 55, a narrow bar 56 welded to vertical plate 54 so the top edge of 56 is approximately flush with the top of plate 54, and a top plate 57 so located as to provide an open space 58 between the bar 56 and one edge of the top plate 57 to form a tow pin guiding slot. 7 I

The roller 51 is mounted between the top plate 57 and the bottom plate 52 with a bolt 60 engaging a nut 61 welded to the bottom of plate 52 and aligned with hole 62 in plate 52 as shown in FIG. 7. A spacer washer 63 is mounted under the top plate 57 above the roller 51 and a hole 64 is provided in the top plate 57 for recessing the head of bolt 60. The roller 51 has an outer cylindrical body 66 with an internal race 67 for a double ball bearing 68. Two similar inner races 69, each having an extension 70 projecting beyond the roller, and a spacer sleeve 71 are mounted on the bolt 60. Seal members 72 in the top and bottom of the roller complete the roller assembly 51. These rollers are so positioned that the edges of chain 40 bear. against these anti-friction rollers while negotiating a horizontal curve to reduce the friction as shown in FIG. 6.

A drive is located at suitable intervals in the path of the conveyor to drive the chain 40. This drive may be a conventional caterpillar drive of a known type so is not shown. Other types of drives suitable for the purpose may be substituted for a caterpillar type drive but do not form part of this invention.

Having described the conveyor system in general and its associated guideways, a description of the preferred embodiment of the chain 40 will now be given. A sequence of elements of the assembled chain is shown in FIGS. 4 and 5 which is repeated throughout the length of the chain wherever engagement with the tow pin 37 on the truck 35 is desired and comprises sections A, B, and C. Section A is connected to section B and to a preceding section A by identical connector links 77, while section B is connected to section C by the special pusher link 42. Section C is connected to a trailing section A by a connector link 77. Each of the sections A, B and C includes an upper and a lower link, all lower links 76 being identical, but the upper links 75, 79 and 80 of the sections A, B and C respectively being of slightly difl'erent design. In general, if the upper link 75 is considered the basic design, link 79 is identical to link 75 except that a rear portion has been cut off, and link 80 is identical to link 75 except that a leading portion has been cut ofi. At portions of the conveyor in which no pusher link is needed, several sections A may be connected in series by connector links 77 as shown in FIGS. 6 and 8. Identical vertical pivot pins 78 couple the upper and lower links of each section with the associated connector links with the exception of the pusher links which are coupled by connector pins 130 of modified design.

In describing a chain that is made up of a plurality of chain links connected end-to-end, it is customary to refer to the chain pitch as the distance on the longitudinal axis of the chain between the centers of adjacent pivot pins or pitch points of the chain. Each chain link thus has two pitch points spaced one chain pitch apart, where holes for the pivot or chain pins are located. In the embodiments of the links used in this invention, the chain pin holes are elongated, having a semi-circular end portion against which the pins bears when the chain is under tension. The pitch point is located at the center of the radius R of this semi-circular portion and is designated P in FIGS. 9-12, 14, 17 and 18. The radius R is slightly greater than the radius of the cylindrical body of the pivot pins. The nominal chain pitch of one well known form of rivetless chain (herein referred to as the standard chain) is 4 inches, although other chain pitches may be used. The overall length of a given link is greater than the chain pitch by the amount of material extending beyond the pitch point on each end and, in the above mentioned standard chain, the links are approximately 5 inches overall in length. A standard rivetless chain is comprised of a pair of identical, spaced apart sidebar links connected in end-to-end relationship to a center link between the sidebars with a chain pin. The sidebar links are relatively thin bar members having a recessed transverse pocket for the heads of the chain pin plus an elongated longitudinal aperture having a length slightly less than twice the body diameter of the chain pin at each pitch point and a web section between the elongated apertures. The center link has an open slot between its pitch points, a central section having a thickness approximately the same as the body diameter of the chain pin and end portions that are approximately 35 percent thicker than the central section. The chain pin has a double projection on each end of its cylindrical body to form an upper and lower head. While this standard pin has been commonly referred to in the industry as having a T-head, it is in reference to an elevational view of the pin in which the body of the pin forms the vertical leg and the two projections of the head form the horizontal legs of the T. Each head thus has only two projections 180 apart; the new pin disclosed herein has three projections 90 apart. The purpose and advantage of this additional projection will be described later. This chain is referred to as a rivetless type since the ends of the chain pin are not riveted over to form a permanent connection as is common on some drive and conveyor chains. Since the conveyors on which rivetless chain is usually applied may extend over several thousand feet, it is desirable to be able to easily disconnect the chain at any point without special tools and any extra manual force. The thinner central thickness of the center link permits the outer sidebars to come together a sufiicient amount to release the pin heads from their recessed pockets in the links so the pin may be rotated 90 and be passed through the elongated apertures for quick and easy removal. When slack occurs in the chain, the open center slot in the center link permits the connected upper and lower sidebar links with their chain pin to slide together or telescope until the ends of adjacent links contact. This permits as much as 2% inches of movement or takeup in the standard rivetless chain. 4 The description to follow will make evident the embodiments of the chain of this invention that differ from the standard chain, to show that the simplicity of the standard is retained while providing new features to meet the requirements of the intended service.

The upper link 75 (FIGS. 9 and is slightly less than two chain pitches long, having each longitudinal end portion extending over the area of the adjacent center links 77 for ap proximately one-half a chain pitch. The top surface 81 of this upper link 75 has substantially smooth and flat portions 81a, 81b and 810 spaced apart by pockets 95 and 96, which will be described presently. The leading end extension 82 of upper links 75 and 79, in the direction of travel, is slanted downwardly toward its end from a point adjacent to the chain pin head. This leading end extension 82 also tapers on its side edges in two steps 84 and 85 of difierent slopes to a small semi-circular projection 86 on its end. The trailing end extension 87 of upper link 75 tapers on its side edges 88 to a small concave arcuate recess or pocket 89. With two adjacent upper links 75 and 75, 75 and 79 or 80 and 75 in their normal operating position under tension, there is approximately inch space between the trailing end extension 87 of one link and the adjacent leading end extension 82 which thus provides about three-sixteenth inch of take-up per chain pitch when these upper links slide together on the open center connector link 77 under slack tension conditions. The semi-circular projection 86 on the leading extension 82 and the arcuate recess 89 in the trailing extension 87 fit together in an approximate mating relationship so that substantial continuity of the top surface of these upper links is maintained whether they are in a straight aligned condition or out of alignment as the chain articulates on a horizontal curve. It is to be noted that the tow pins 37 normally used are approximately 1 inch in diameter so they will easily ride over the above inch minimum space between links without jamming. This condition is illustrated in FIGS. 4 and 6. FIG. 6 also shows the purpose of the tapering of the side edges of the extensions 82 and 87 of the upper links. The vertical wall plate 54 (FIG. 7) of the chain guideway in a horizontal roller turn 50 is located in the same relationship to the centerline of the chain as in a straight section (FIG. 2) so interference or rubbing of these link side edges 84, 85 and 88 on the turn is eliminated.

As shown in FIGS. 9 and 10, the extensions 82 and 87 of the upper link 75 also have vertically depending curved lip portions 90 and 91 on the leading and trailing projections respectively. These lips provide abutment surfaces so that, when adjacent upper links 75, 79 and 80 slide together under a slack tension condition on the horizontal or on a vertical curve, any possible overlapping of these links is prevented and the smooth continuity of the upper surface is maintained. When the upper links 75 articulate on a vertical curve, as shown in FIG. 8, the downwardly slanted end of the leading projection provides a smooth transition between a leading link and a trailing link, thereby preventing an obstruction for the smooth sliding of the tow pin 37 over this joint.

Two T-shaped pockets 95 and 96 are provided in the upper link to receive the chain pins 78 at each pitch point, P, which is located at the center of the radius R of a semi-circular end portion of a longitudinal aperture in each pocket as shown in FIGS. 9 and 10. These pockets are spaced in from each end extension 82 and 87 symmetrically from the mid-point of the link so the chain pins will be separated a distance equal to the chain pitch. Each pocket consists of a transverse portion 97 recessed from the top surface of the link about 40 percent of its total thickness and a longitudinally slotted aperture 98 on the centerline of the link. The width of the transverse recessed portion and the width of the longitudinal slot are slightly larger than the diameter of the cylindrical body 99 (FIG. 8) of the chain pin. The transverse recess portion extends across the full width of the link. The length of the longitudinal slot is slightly greater than the diameter of the body 99 of the pin 78 extending toward the mid-point of the link from the pitch point, P, (FIG. 9) which is located at the center of radius R from the end of the semi-circular portion 100 of the longitudinal slot 98.

Pivot pins 78 have a special head construction, as shown in FIGS. l9-22. The body 99 of the pin is cylindrical; the upper head 101 is T-shaped; and the lower head is I-shaped. The upper head 101 has three fingerlike shoulders or projections 102, each spaced 90 apart and each extending from the centerline of the pin a distance approximately equal to the diameter of the body 99. The lower head 103 has two projections 104 180 apart, each extending from the centerline of the pin a distance approximately equal to the diameter of the cylindrical body 99. When each pin 78 is assembled in the chain, the upper head 101 fits into the mating T-shaped pocket 95 or 96 of the upper link 75 and the lower head 103 fits into pockets 105 (FIGS. 11 and 12) of the lower link 76 so that the top of the pin is approximately flush with the top surface 81 of the upper link and the bottom of the pin is approximately flush with the bottom surface of the lower link at the pin. The upper T-shaped head substantially closes the slotted aperture 98 in the upper link 75 to maintain the continuity of the smooth upper surface of this link. The slotted aperture 98 in the upper link provides space for the lower double projection during removal of the chain pin 78 after the pin has been rotated 90 so the lower head is in alignment with this aperture, as will be described later.

The two pockets 105 of each lower link 76, shown in FIGS. 11-13, are recessed from the bottom surface of the link. A slotted aperture 107, whose length is slightly less than twice the diameter of the body 99 of the pin 78 extending from the pitch point, P, is included at each pocket 105 on the centerline of the link. These pockets are symmetrically spaced from the mid-point of the link so the pivot pins will be separated at a distance equal to the chain pitch, but the overall length of the link is substantially the same as the length of a standard link or only slightly longer than the chain pitch as compared to the upper link 75, which is considerably longer. Between the slotted apertures 107, the central portion 108 of this link 76 is solid across the full width of the link. and projects below the lower surface of the end portions of this link to provide a relatively large area wean'ng surface 109 for the chain to slide upon. Beveled rib portions 110 extend along the sides of the slotted apertures 107 to the transverse recessed portions 106 of the chain pin pockets 105 to provide a smooth transition to the lower wearing surface portion. Since the heads of the pivot pins 78 are recessed in the lower link 76, this lower wearing surface 109 is substantially below the heads of the pivot pins so there is no danger of these heads wearing as the chain slides.

Each connector link 77 is a conventional standard center link. As shown in FIGS. 4 and 5, this link has a longitudinal aperture 112 extending between the pitch points of'the chain with semi-circular end portions 113. The width of the aperture 112 is'slight greater than the diameter of the cylindrical body 99 of the pivot pin. The overall length of the link 77 is slightly longer than the chain pitch and the same as the length of the lower link 76. The end portions 114 of the center link have thickened projections 115 on thetop and bottom surfaces, which are convex, while the central portion is approximately the same thickness as the diameter of the body 99 of the pin. The rounded end projections permit the chain to flex in the vertical plane, as shown in FIG. 8, as well as in the horizontal plane.

The pusher link 42, as shown in FIGS. 14-16, comprises a body member 119, substantially identical in construction to a link 77, and a L-shaped dog member 120 welded to the body member, the dog having a cross-shaped pushing face 43 for contacting the tow pin 37 of the truck. The L-shaped dog member 120 has a narrow rectangular block portion 122, which fits through the slotted aperture 112 of the connector link and projects below this link to a point just slightly above the plane of the bottom of the wearing surface 109 of the lower link 76. As seen in FIGS. 4 and 5, the pushing face 43 of member 120 projects vertically above the top surface of upper link 79 and 80 at approximately the mid-point of the body member 119. The face 43 and the top surface 123 of the block portion 122 cooperate with the rear end of adjacent upper link 79 to provide a pocket 74 below the top surface of the adjacent upper link for the tow pin to drop into. The arms 124 of the cross extend to the full width of the center link and are tapered slightly toward the rear of the link. The block portion 122 of member 120 is located centrally on the body member and has a length such that .a smaller aperture 125, whose length is slightly less than twice the diameter of the body 132 of pin 130 extending from the pitch point, P, is left at each end to receive a vertical pivot pin.

Since a pocket is desired at the pusher link 42 to receive the tow pin 37, the upper links adjacent the pusher link 42 do not have the end extensions 82 and 87 of the upper link 75. Specifically, the link 79 is the same as upper link 75 except that the trailing end extension 87 of link 75 is eliminated slightly beyond the recessed pocket for the pivot pin. Trailing upper link 80 is also the same as upper link 75 except that the leading end extension 82 of link 75 is eliminated slightly beyond the recessed pocket for the pivot pin. Links 79 and 80 may be made from regular upper links 75 by cutting off extension 87 or 82.

In order to facilitate the insertion or removal of a pusher link in a length of assembled chain, the chain pins that are used on either side of the pusher assembly 42 are different in design than pins 78. As shown in FIGS. 23-25, each chain pin 130 has an upper T-shaped head 131 having three fingerlike shoulders or projections similar to that of pin 78 but does not have a lower double head. The cylindrical body 132 of pin 130 is extended to the equivalent overall length of pin 78. A small diameter hole 133 is drilled through this cylindrical body near the bottom end perpendicular to the axis of the pin and parallel to the double projections on the upper head. After the pin 130 is inserted in the assembled chain a curled, tubular pin 134, commonly referred to as a rollpin and having a length approximately the same as the width of lower link 76, is inserted in hole 133 to lock the assembled chain.

A second embodiment 135 of a pusher link is shown in FIGS. 17 and 18. This link is used where the desired spacing of pusher assemblies is such that the pusher element must be mounted on an upper link rather than on a connector link. This pusher link 135 comprises an upper link 136, the same as upper link 75, and a trapezoidal block member 137 welded to the top surface of the upper link at approximately the midpoint of the link 136. This member 137 has a vertical face 138 projecting above the top surface of link 136 to the same plane as the top of the cross-shaped pushing face 43 of pusher link 42 and normal to the longitudinal axis of the link 136.

A second embodiment of the lower link is shown in FIGS. 26-29. This lower link assembly 140 comprises a conventional rivetless chain sidebar link 141 having a transverse recess and an elongated longitudinal aperture at each pitch point and a web section between the apertures, a low friction replaceable wearing shoe 142 and fastening means 143 for securing the wearing shoe to the sidebar 141, such as a countersunk head machine screw threaded into the wearing shoe. The wearing shoe 142 may be made of a plastic material, such as Delrin, an oil filled porous bronze or similar material having low sliding friction properties and long life. The upper portion 144 of the wearing shoe is shaped to fit within the rectangular relieved pocket in the central portion of the conventional sidebar under the web portion 145 and be held from rotation by the mating shape of the upper portion with this pocket. The lower portion of the wearing shoe 146 extends transversely for the full width of the sidebar 141 and projects below the end portion 147 of the standard sidebar thickness and the heads of the pivot pins 78 to provide a relatively large area for the chain to slide upon in the same manner as lower link 76.

The primary purpose of the combination of new elements in chain 40 is to provide a smooth continuous surface on top of the chain for the tow pin 37 to pass over without interruption or catching until it reaches pocket 74 just ahead of the pushing face 43 of the pusher link. Engagement of the tow pin with the pusher provides the propelling contact for moving the truck. This requires the upper link itself to be free of discontinuities and means for maintaining this plane of contact with the tow pin over the area of the connector link 77 whose level is lower. By having the end extensions 82 and 87, with their respective mating semi-circular ends 86 and 89, this plane of contact is maintained above the connector link 77, as shown in FIGS. 4

and 5. Without these extensions, the tow pin would drop into a pocket similar to that of pocket 74 at every other pitch. When the chain articulates in a horizontal plane, as shown in FIG. 6, the tapered side edges of extensions 82 and 87 cooperate with the guideway to enable the chain with these extensions to negotiate a curve without requiring additional width in the guideway and to still maintain the continuous contact surface for the tow pin. When the chain articulates in a vertical plane, as shown in FIG. 8, the beveled end of the leading extension 82, projecting beyond the articulation point and the mating semi-circular ends 86 and 89, prevents an obstruction to the sliding of the tow pin as the pin slides ofi end 87 onto end 82. Upper links 75,79 and 80 are provided with T-shaped pockets 95 and 96 for pivot pins 78 or 130. The pin heads are recessed in these pockets so the tops of the pins are flush with the top of the link. Pins 78 and 130 have upper heads with triple projections so that, when assembled in the upper links, the T-shaped pockets are substantially filled and the continuity of the upper surface of the link is maintained. With the standard chain and pin, a gap is left in the upper sidebar link by the double projection on the pin not filling the elongated aperture required for removal of the pin.

Due to the inherent looseness and flexibility of this chain, so as to bend in either the horizontal or vertical planes, into the continuous slot in the connector link 77, when slack accumulates, such as just ahead of a drive engagement point, the end extension 82 of adjacent upper links 75 might tend to slide under extension 87 into an overlapping condition unless otherwise prevented. The applicants invention prevents this by providing novel lip portions 90 and 91 depending from the underside of the semi-circular end portions 86 and 89 respectively. These mating rounded lips 90 and 91 provide abutment surfaces of sufficient thickness that overlapping of the adjacent upper links is prevented. Clearance is still provided for about three-sixteenths of an inch of horizontal movement or takeup per chain pitch, or three-eighths of an inch per upper link having an equivalent length of two pitches, but this amount is well within the capability of the usual 1 inch diameter tow pin to slide over. With the usual application of the standard chain, the tow pin does not contact the top of the chain directly, so this problem of obstructing the free passage of the tow pin does not occur.

With the disclosed improvements, the same number of basic elements, as in the standard rivetless chain comprising a pair of upper and lower links, a connector link and a chain pin, is retained, but the additional features and advantages described above have been provided for to obtain a chain suitable for operating within the limited confines of a lower profile conveyor guideway.

The manner of removal or assembly of pivot pins 78 will now be described. The connector link 77 has a narrow central section 116 with an open slot 112 between the chain pins. When the center link is turned at a sharp angle from its normal position, the adjacent upper and lower links 75 and 76 with their pivot pin 78 can slide down the connector link to this thinner central portion 116. The ends of the upper and lower links can then be brought closer together an amount that permits both heads of pin 78 to be free of their pockets 95 and 96 in link 75 and pocket 105 in link 76. The lower head 103 of pin 78 can then be turned 90 so it is parallel with the longitudinal centerline of the upper and lower links. In this position the lower head of the pin can then pass up through the aperture 107 in the bottom link 76, the slotted aperture 112 in the center link 77 and the T-shaped pocket 95 or 96 in the upper link 75. Since the aperture 98 in the upper link 75 is intentionally shorter than aperture 107 in the lower link, so the upper head of the pivot pin 78 will more closely fill the opening, pin 78 has to be tilted slightly after being removed from link 76 to withdraw the pin through the upper link 75.

Although the best mode contemplated for carrying out the present invention has been shown and described herein, it will be apparent that modification and variation may be made without departing from what is regarded the subject matter of the invention.

What is claimed is:

1. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises:

a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls;

b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pin having a body and an upper head comprising at least three shoulders projecting horizontally beyond the body of said pin, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for matingly receiving the upper head of each pivot pin, said upper head substantially closing said pocket, whereby the top surface of adjacent upper links extends over the area of the connector link and presents a substantially continuous surface for the tow pin to ride over without entanglement;

c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the' direction of travel of the chain; and

d. drive means interconnected with the chain for propelling the chain.

2. The conveyor of claim 1, wherein said guideway further comprises a bar member secure to the inside of the upper ends of each vertical flange of said U-shaped guideway to form said slot for said tow pin and a plate member secured to the inside of the bottom horizontal portion of said guideway to form a wearing member for said chain to slide upon.

3. The conveyor of claim 1, wherein said chain is of the rivetless type and is endless, and where said pivot pins are vertical.

4. The conveyor of claim 1, wherein said lower link has a central portion with beveled ends which projects substantially below the lower head of said pivot pins and said central portion extends substantially over the area between the pivot pins to provide a large planar surface to support the chain while it is sliding on the bottom of said guideway.

5. The conveyor of claim 1, wherein the upper links of said chain further have a rounded leading end and an arcuate pocket in the trailing end whereby the trailing end and the leading end of two adjacent upper links fit in a mating relationship and substantially retain this relationship as the chain articulates around a horizontal curve.

6. In a chain having a series of sections connected in an endless array, each section comprising a pair of upper and lower links, a connector link disposed vertically between said pair of links in end-toend relationship, and a pivot pin coupling said links, the improvement which comprises extension means on each end of said upper link, each extension having a length of approximately one-half of a chain pitch, whereby adjacent upper links extend over the area of said connector link and form a substantially smooth and continuous top surface on said chain.

7. In a chain of the type wherein a plurality of elongated links comprising a pair of upper and lower links and a connector link vertically disposed therebetween are connected to form an endless array with adjacent upper links being capable of limited movement toward and away from each other and with the leading edge of each upper link being in adjacent confronting relation with the trailing edge of the preceding link and disposed in substantially the same horizontal plane, the improvement which comprises means providing an abutment member projecting downwardly from at least one of said confronting edges of an adjacent pair of upper links a distance sufficient to prevent telescoping of said upper links during move ment and means for guiding said endless array of links for movement along a curved path in a vertical plane.

8. In a chain of the type having a section comprising three elongated links disposed in a generally parallel superposed relation, means defining a slot in each link elongated along the length of the link and aligned with the slots in the other two links, and a pin extending through said slots and having a transverse member at one end that is longer than said slots are wide, whereby said member is movable through said slots when disposed generally parallel thereto and is not movable therethrough when oriented transversely to said slots, the uppermost of said links having a recess on its upper surface extending transversely to the slot in said uppermost link, the improvement which comprises means defining a head on the end of said pin opposite said one end having the transverse member, said head having a first portion engaging said transverse recess in said uppermost link and a second portion overlying the longitudinal slot in said uppermost link, the upper surface of said head being substantially flush with the upper surface of said uppermost link and said first and second portions of said head substantially covering said transverse recess and said longitudinal slot respectively to provide a substantially continuous smooth upper surface on the uppermost link.

9. An endless rivetless type conveyor chain which comprises:

a. a plurality of upper horizontal links, each link having a forward end extending beyond a first pitch point of said link for a distance approximately one-half a chain pitch with the sides narrowing to a semi-circular end portion, a first abutment depending from the semi-circular end portion on the underside of the link, and its top surface beveled toward the end, the link having a rear end extending beyond a second pitch point approximately onehalf a chain pitch, its sides narrowing to an arcuate pocket, and a second abutment depending from the arcuate pocket on the underside of the link;

b. a plurality of lower horizontal links vertically spaced apart from said upper links to form link pairs with said upper links, each of said lower links having a central portion projecting below the end portions of said lower links, providing a bottom wearing surface of substantial area;

0. a plurality of connector links disposed vertically between said upper and lower links; and

d. means connecting said link pairs and said connector links in substantial end-to-end overlapping relationship.

10. The conveyor chain of claim 9, wherein said upper links have a T-shaped pocket at each of its two pitch points and said connecting means comprises a vertical pivot pin having an upper head portion with three horizontal projections each spaced 90 apart, whereby said head portion substantially fills the T-shaped pocket in said upper links when the pin is assembled in these pockets to maintain a substantially unbroken upper surface of the chain.

11. The conveyor chain of claim which further comprises:

a. at least one pusher link connected in said chain including an elongated body member having two elongated slots and a pusher dog secured thereto and having a vertical face between the slots extending above the plane of the top of said upper links;

b. a leading upper link adjacent said pusher link, having a T- shaped pocket at each of the first and second pitch points of said upper link, said upper link having a forward end extending beyond the first pitch point approximately onehalf of the chain pitch and sides narrowing to a semi-circular end portion, an abutment depending from the semicircular end portion on the underside of said upper link, the top surface of said end portion beveled toward the end, and said upper link having a rear end portion extending only a minimum distance beyond the second pitch point and the T-shaped pocket, whereby a pocket is formed between the rear end portion of said leading upper link and the pusher dog;

c. a trailing upper link adjacent said pusher link having a T- shaped pocket at each of the first and second pitch points of said trailing upper link, said trailing link having a rear end extending beyond the second pitch point approximately one-half a chain pitch and sides narrowing to an arcuate pocket, and an abutment depending from the arcuate pocket on the underside of said trailing link, and said trailing link having a forward end portion extending only a minimum distance beyond the first pitch point and the T-shaped pocket;

d. two lower horizontal links parallel to and vertically spaced apart from said leading and trailing links to form leading and trailing link pairs, said lower links having a central portion projecting below its end portions of said links providing a bottom wearing surface of substantial area;

e. a vertical pivot pin at each pitch point of said pusher link interconnecting said leading and trailing link pairs with said pusher assembly in overlapping but substantially endto-end relationship, said pivot pin having an upper head portion with three horizontal projections each spaced apart and a cylindrical body portion having a horizontal hole therethrough near its bottom end; and

f. a locking pin having a length greater than the diameter of the body portion of the chain pin inserted in the hole in each pivot pin after assembly of said link pairs with said pusher link.

12. An endless rivetless type conveyor chain which comprises:

a. a plurality of upper horizontal links having a forward end extending beyond the first pitch point of the link approximately one-half of the chain pitch having its sides narrowing to a semi-circular end portion and a rear end extending beyond the second pitch point of the link approximately one-half a chain pitch having its sides narrowing to an arcuate pocket, the forward semi-circular end portion having a depending first abutment on the underside of the link and the rear arcuate pocket having a depending second abutment around said pocket on the underside of the link;

b. a plurality of lower horizontal links vertically spaced apart from the upper links to form link pairs with said upper links, said lower links comprising an outer sidebar link having an elongated aperture and a transverse recess on the underside of said link at each of its two pitch points and a central web member between these apertures whose top surface is flush with the top surface of the sidebar but relieved on the underside to form a recess, said web further having a central hole therethrough, a replaceable wearing shoe having an upper portion of a shape to be matingly received in said recess and a lower portion projecting below the bottom of the sidebar, having a length approximately equal to the length of the central web member of the sidebar to provide a bottom wearing surface of substantial area, and means for removably securing said wearing shoe to said sidebar;

c. a plurality of connector links disposed vertically between said upper and lower links; and

d. means connecting said link pairs and said connector links in substantial end-to-end overlapping relationship.

13. An upper link for a rivetless type conveyor chain in which the pivot pins at each of the two pitch points of the link are vertical which comprises: a horizontal member with a substantially solid top surface having a length slightly less than twice the chain pitch and a T-shaped pocket with a transverse recess on the upper side of said upper link and an elongated aperture therethrough at each pitch point; a forward end extending beyond the first pitch point of the link approximately one-half of the chain pitch having its sides narrowing to a semi-circular end portion; a rear end extending beyond the second pitch point approximately one-half of a chain pitch having its sides narrowing to an arcuate pocket; the forward end portion further having a depending first abutment on the underside of the link; the rear arcuate pocket further having a depending second abutment around said arcuate pocket on the underside of the link; and said forward end further having its top surface beveled toward the semi-circular end portion.

14. The upper link of chain 13 which further comprises a block member secured to the top surface of said upper link between the elongated apertures, said member having a vertical face transverse to the longitudinal axis of said link and extending above the top surface of the upper link to form a pusher link.

15. In a pivot pin for a rivetless type conveyor chain, said pin having a cylindrical body portion and a lower head having two projecting flanges spaced 180 apart, the improvement which comprises an upper head perpendicular to said body portion and having three projecting flanges of equal length each spaced 90 apart.

16. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises:

a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls;

b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin further comprising an upper head having three projections each spaced 90 apart, a lower head having two projections each spaced 180 apart and a cylindrical body section connecting the upper and lower heads of said pin and perpendicular thereto, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T- shaped pocket at each chain pitch point for receiving the upper head of each pivot pin, whereby the top surface of adjacent upper links extends over the area of the connector link and presents a substantially continuous surface for the tow pin to ride over;

c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and

d. drive means interconnected with the chain for propelling the chain.

17. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises:

a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls;

b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin further comprising an upper head having three projections each spaced 90 apart, a cylindrical body perpendicular to the projections having a hole therethrough adjacent its lower end and parallel to the two projections each spaced 180 apart and a locking pin in said hole having a length slightly longer than the diameter of the cylindrical body of said pivot pin, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T- shaped pocket at each chain pitch point for receiving the head of each pivot pin;

c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and

d. drive means interconnected with the chain for propelling the chain.

18. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises:

a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in a plane on which the truck rolls;

b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin having a head with three fingerlike shoulders at its upper end, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for receiving the head of each pivot pin, said upper links of said chain further having a rounded leading end and an arcuate pocket in the trailing end whereby the trailing end and the leading end of two adjacent upper links fit in a mating relationship and substantially retain this relationship as the chain articulates around a horizontal curve, said upper links further including a first curved vertical abutment depending from the underside of said rounded leading end and a second curved vertical abutment depending from the underside of said arcuate pocket in the trailing end, both of said abutments following the curve and being flush with their respective outer ends;

c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and

d. drive means interconnected with the chain for propelling the chain.

19. The conveyor according to claim 18, wherein the leading end of said upper link further has its top surface beveled toward the end.

20. The conveyor according to claim 19, wherein the leading and trailing ends of said upper link extending beyond the pitch point of said link have their side edges tapering to their respective rounded end and arcuate pocket.

21. In a chain having a series of sections connected in an endless array, each section comprising a pair of upper and lower links, a connector link disposed vertically between said pair of links in an end-to-end relationship and a pivot pin coupling said links, the improvement which comprises extension means on each end of said upper link, each extension means having a length of approximately one-half of a chain pitch, said extension means comprising a leading extension with the sides narrowing to a semi-circular end portion and the top surface beveled downwardly toward the semi-circular end portion and a trailing end extension with the sides narrowing to an arcuate pocket, whereby adjacent upper links extend over the area of said connector link, said leading end semi-circular portion at least partially fitting within said trailing end arcuate pocket of an adjacent upper link to substantially main tain the continuity of the smooth top surface of said upper links whether the links are aligned in a straight path or are articulated on a horizontal curve.

22. The chain according to claim 21, wherein said lower link has a central portion which projects substantially below the lower end of said pivot pins substantially over the area between adjacent pivot pins in said lower link to provide a large planar surface to support the chain during its movement.

23. In a chain of the type wherein a plurality of elongated links are connected to form an endless array, said links including at least a pair of upper and lower links and a connector link disposed vertically between said pair of links, said upper adjacent links being capable of limited movement toward and away from each other and with the leading end of each upper link being in adjacent confronting relation with the trailing end of the preceding link and disposed in the same horizontal plane, the improvement which comprises said upper link having an overall length of approximately two chain pitches including an extension on each of its ends approximately onehalf a chain pitch in length, a first extension having the sides tapering to a semi-circular end portion on one end of said upper link and a second extension having the sides tapering to an arcuate pocket on the other end of said upper link, said first extension having a curved lip projecting downwardly from the semi-circular end portion and said second extension having a curved lip projecting downwardly from the arcuate pocket, said lips projecting a distance sufficient to prevent telescoping of said upper links during movement of said endless array of links along a curved path in a vertical plane.

24. In a chain of the type having a section comprising three elongated links disposed in generally parallel superposed relation, means defining a slot in each link elongated along the length of the link and aligned with the slots in the other two links, and a pin extending through said slots connecting said links and having a transverse member at one end that is longer than said slots are wide, whereby said member is movable through said slots when disposed generally parallel thereto and is not movable therethrough when oriented transversely to said slots, the uppermost of said links having a recess on its upper surface extending transversely to the elongated slot in said uppermost link, the improvement which comprises a head on the other end of said pin opposite said one end of pin having said transverse member, said head having three equal projections spaced apart, perpendicular to the longitudinal length of said pin and each projection having a length from the center of the pin approximately equal to the diameter of said pin, said head having a transverse portion formed by two of said three projections apart overlying said transverse recess and said third projection overlying said longitudinal slot in said uppermost link, the upper surface of said head being substantially flush with the upper surface of said uppermost link to provide a substantially smooth continuous upper surface. 

1. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises: a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls; b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pin having a body and an upper head comprising at least three shoulders projecting horizontally beyond the body of said pin, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for matingly receiving the upper head of each pivot pin, said upper head substantially closing said pocket, whereby the top surface of adjacent upper links extends over the area of the connector link and presents a substantially continuous surface for the tow pin to ride over without entanglement; c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and d. drive means interconnected with the chain for propelling the chain.
 2. The conveyor of claim 1, wherein said guideway further comprises a bar member secure to the inside of the upper ends of each vertical flange of said U-shaped guideway to form said slot for said tow pin and a plate member secured to the inside of the bottom horizontal portion of said guideway to form a wearing member for said chain to slide upon.
 3. The conveyor of claim 1, wherein said chain is of the rivetless type and is endless, and where said pivot pins are vertical.
 4. The conveyor of claim 1, wherein said lower link has a central portion with beveled ends which projects substantially below the lower head of said pivot pins and said central portion extends substantially over the area between the pivot pins to provide a large planar surface to support the chain while it is sliding on the bottom of said guideway.
 5. The conveyor of claim 1, wherein the upper links of said chain further have a rounded leading end and an arcuate pocket in the trailing end whereby the trailing end and the leading end of two adjacent upper links fit in a mating relationship and substantially retain this relationship as the chain articulates around a horizontal curve.
 6. In a chain having a series of sections connected in an endless array, each section comprising a pair of upper and lower links, a connector link disposed vertically between said pair of links in end-to-end relationship, and a pivot pin coupling said links, the improvement which comprises extension means on each end of said upper link, each extension having a length of approximately one-half of a chain pitch, whereby adjacent upper links extend over the area of said connector link and form a substantially smooth and continuous top surface on said chain.
 7. In a chain of the type wherein a plurality of elongated links comprising a pair of upper and lower links and a connector link vertically disposed therebetween are connected to form an endless array with adjacent upper links being capable of limited movement toward and away from each other and with the leading edge of each upper link being in adjacent confronting relation with the trailing edge of the preceding link and disposed in substantially the same horizontal plane, the improvement which comprises means providing an abutment member projecting downwardly from at least one of said confronting edges of an adjacent pair of upper links a distance sufficient to prevent telescoping of said upper links during movement and means for guiding said endless array of links for movement along a curved path in a vErtical plane.
 8. In a chain of the type having a section comprising three elongated links disposed in a generally parallel superposed relation, means defining a slot in each link elongated along the length of the link and aligned with the slots in the other two links, and a pin extending through said slots and having a transverse member at one end that is longer than said slots are wide, whereby said member is movable through said slots when disposed generally parallel thereto and is not movable therethrough when oriented transversely to said slots, the uppermost of said links having a recess on its upper surface extending transversely to the slot in said uppermost link, the improvement which comprises means defining a head on the end of said pin opposite said one end having the transverse member, said head having a first portion engaging said transverse recess in said uppermost link and a second portion overlying the longitudinal slot in said uppermost link, the upper surface of said head being substantially flush with the upper surface of said uppermost link and said first and second portions of said head substantially covering said transverse recess and said longitudinal slot respectively to provide a substantially continuous smooth upper surface on the uppermost link.
 9. An endless rivetless type conveyor chain which comprises: a. a plurality of upper horizontal links, each link having a forward end extending beyond a first pitch point of said link for a distance approximately one-half a chain pitch with the sides narrowing to a semi-circular end portion, a first abutment depending from the semi-circular end portion on the underside of the link, and its top surface beveled toward the end, the link having a rear end extending beyond a second pitch point approximately one-half a chain pitch, its sides narrowing to an arcuate pocket, and a second abutment depending from the arcuate pocket on the underside of the link; b. a plurality of lower horizontal links vertically spaced apart from said upper links to form link pairs with said upper links, each of said lower links having a central portion projecting below the end portions of said lower links, providing a bottom wearing surface of substantial area; c. a plurality of connector links disposed vertically between said upper and lower links; and d. means connecting said link pairs and said connector links in substantial end-to-end overlapping relationship.
 10. The conveyor chain of claim 9, wherein said upper links have a T-shaped pocket at each of its two pitch points and said connecting means comprises a vertical pivot pin having an upper head portion with three horizontal projections each spaced 90* apart, whereby said head portion substantially fills the T-shaped pocket in said upper links when the pin is assembled in these pockets to maintain a substantially unbroken upper surface of the chain.
 11. The conveyor chain of claim 10 which further comprises: a. at least one pusher link connected in said chain including an elongated body member having two elongated slots and a pusher dog secured thereto and having a vertical face between the slots extending above the plane of the top of said upper links; b. a leading upper link adjacent said pusher link, having a T-shaped pocket at each of the first and second pitch points of said upper link, said upper link having a forward end extending beyond the first pitch point approximately one-half of the chain pitch and sides narrowing to a semi-circular end portion, an abutment depending from the semi-circular end portion on the underside of said upper link, the top surface of said end portion beveled toward the end, and said upper link having a rear end portion extending only a minimum distance beyond the second pitch point and the T-shaped pocket, whereby a pocket is formed between the rear end portion of said leading upper link and the pusher dog; c. a trailing upper link adjacent said pusher link having a T-shaPed pocket at each of the first and second pitch points of said trailing upper link, said trailing link having a rear end extending beyond the second pitch point approximately one-half a chain pitch and sides narrowing to an arcuate pocket, and an abutment depending from the arcuate pocket on the underside of said trailing link, and said trailing link having a forward end portion extending only a minimum distance beyond the first pitch point and the T-shaped pocket; d. two lower horizontal links parallel to and vertically spaced apart from said leading and trailing links to form leading and trailing link pairs, said lower links having a central portion projecting below its end portions of said links providing a bottom wearing surface of substantial area; e. a vertical pivot pin at each pitch point of said pusher link interconnecting said leading and trailing link pairs with said pusher assembly in overlapping but substantially end-to-end relationship, said pivot pin having an upper head portion with three horizontal projections each spaced 90* apart and a cylindrical body portion having a horizontal hole therethrough near its bottom end; and f. a locking pin having a length greater than the diameter of the body portion of the chain pin inserted in the hole in each pivot pin after assembly of said link pairs with said pusher link.
 12. An endless rivetless type conveyor chain which comprises: a. a plurality of upper horizontal links having a forward end extending beyond the first pitch point of the link approximately one-half of the chain pitch having its sides narrowing to a semi-circular end portion and a rear end extending beyond the second pitch point of the link approximately one-half a chain pitch having its sides narrowing to an arcuate pocket, the forward semi-circular end portion having a depending first abutment on the underside of the link and the rear arcuate pocket having a depending second abutment around said pocket on the underside of the link; b. a plurality of lower horizontal links vertically spaced apart from the upper links to form link pairs with said upper links, said lower links comprising an outer sidebar link having an elongated aperture and a transverse recess on the underside of said link at each of its two pitch points and a central web member between these apertures whose top surface is flush with the top surface of the sidebar but relieved on the underside to form a recess, said web further having a central hole therethrough, a replaceable wearing shoe having an upper portion of a shape to be matingly received in said recess and a lower portion projecting below the bottom of the sidebar, having a length approximately equal to the length of the central web member of the sidebar to provide a bottom wearing surface of substantial area, and means for removably securing said wearing shoe to said sidebar; c. a plurality of connector links disposed vertically between said upper and lower links; and d. means connecting said link pairs and said connector links in substantial end-to-end overlapping relationship.
 13. An upper link for a rivetless type conveyor chain in which the pivot pins at each of the two pitch points of the link are vertical which comprises: a horizontal member with a substantially solid top surface having a length slightly less than twice the chain pitch and a T-shaped pocket with a transverse recess on the upper side of said upper link and an elongated aperture therethrough at each pitch point; a forward end extending beyond the first pitch point of the link approximately one-half of the chain pitch having its sides narrowing to a semi-circular end portion; a rear end extending beyond the second pitch point approximately one-half of a chain pitch having its sides narrowing to an arcuate pocket; the forward end portion further having a depending first abutment on the underside of the link; the rear arcuate pocket further having a depending second abutment around said arcuate pockeT on the underside of the link; and said forward end further having its top surface beveled toward the semi-circular end portion.
 14. The upper link of chain 13 which further comprises a block member secured to the top surface of said upper link between the elongated apertures, said member having a vertical face transverse to the longitudinal axis of said link and extending above the top surface of the upper link to form a pusher link.
 15. In a pivot pin for a rivetless type conveyor chain, said pin having a cylindrical body portion and a lower head having two projecting flanges spaced 180* apart, the improvement which comprises an upper head perpendicular to said body portion and having three projecting flanges of equal length each spaced 90* apart.
 16. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises: a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls; b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin further comprising an upper head having three projections each spaced 90* apart, a lower head having two projections each spaced 180* apart and a cylindrical body section connecting the upper and lower heads of said pin and perpendicular thereto, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for receiving the upper head of each pivot pin, whereby the top surface of adjacent upper links extends over the area of the connector link and presents a substantially continuous surface for the tow pin to ride over; c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and d. drive means interconnected with the chain for propelling the chain.
 17. A conveyor system for propelling a wheel supported truck having a vertically movable tow pin mounted thereon, the combination which comprises: a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in the plane on which the truck rolls; b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin further comprising an upper head having three projections each spaced 90* apart, a cylindrical body perpendicular to the projections having a hole therethrough adjacent its lower end and parallel to the two projections each spaced 180* apart and a locking pin in said hole having a length slightly longer than the diameter of the cylindrical body of said pivot pin, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for receiving the head of each pivot pin; c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and d. drive means interconnected with the chain for propelling the chain.
 18. A conveyor system for propelling a wheel supported tRuck having a vertically movable tow pin mounted thereon, the combination which comprises: a. a U-shaped chain guideway having an upper central slot restricted in width to receive said tow pin, the top of said guideway being in a plane on which the truck rolls; b. a chain operable in said guideway, including a pair of horizontal upper and lower links vertically spaced apart, a horizontal connector link disposed vertically between said upper and lower links in overlapping relationship and a pivot pin connecting said link pair and said connector link, said pivot pin having a head with three fingerlike shoulders at its upper end, said upper link having a continuous smooth top surface, an overall length slightly less than twice the chain pitch and a T-shaped pocket at each chain pitch point for receiving the head of each pivot pin, said upper links of said chain further having a rounded leading end and an arcuate pocket in the trailing end whereby the trailing end and the leading end of two adjacent upper links fit in a mating relationship and substantially retain this relationship as the chain articulates around a horizontal curve, said upper links further including a first curved vertical abutment depending from the underside of said rounded leading end and a second curved vertical abutment depending from the underside of said arcuate pocket in the trailing end, both of said abutments following the curve and being flush with their respective outer ends; c. at least one pusher assembly connected in said chain having a vertical pushing face extending above the plane of the top of said upper links for engaging the tow pin to enable the chain to push the truck in the direction of travel of the chain; and d. drive means interconnected with the chain for propelling the chain.
 19. The conveyor according to claim 18, wherein the leading end of said upper link further has its top surface beveled toward the end.
 20. The conveyor according to claim 19, wherein the leading and trailing ends of said upper link extending beyond the pitch point of said link have their side edges tapering to their respective rounded end and arcuate pocket.
 21. In a chain having a series of sections connected in an endless array, each section comprising a pair of upper and lower links, a connector link disposed vertically between said pair of links in an end-to-end relationship and a pivot pin coupling said links, the improvement which comprises extension means on each end of said upper link, each extension means having a length of approximately one-half of a chain pitch, said extension means comprising a leading extension with the sides narrowing to a semi-circular end portion and the top surface beveled downwardly toward the semi-circular end portion and a trailing end extension with the sides narrowing to an arcuate pocket, whereby adjacent upper links extend over the area of said connector link, said leading end semi-circular portion at least partially fitting within said trailing end arcuate pocket of an adjacent upper link to substantially maintain the continuity of the smooth top surface of said upper links whether the links are aligned in a straight path or are articulated on a horizontal curve.
 22. The chain according to claim 21, wherein said lower link has a central portion which projects substantially below the lower end of said pivot pins substantially over the area between adjacent pivot pins in said lower link to provide a large planar surface to support the chain during its movement.
 23. In a chain of the type wherein a plurality of elongated links are connected to form an endless array, said links including at least a pair of upper and lower links and a connector link disposed vertically between said pair of links, said upper adjacent links being capable of limited movement toward and away from each other and with the leading end of each upper link being in adjacent confronting relation with the trailing end of the preceding link and disposed in the same horizonTal plane, the improvement which comprises said upper link having an overall length of approximately two chain pitches including an extension on each of its ends approximately one-half a chain pitch in length, a first extension having the sides tapering to a semi-circular end portion on one end of said upper link and a second extension having the sides tapering to an arcuate pocket on the other end of said upper link, said first extension having a curved lip projecting downwardly from the semi-circular end portion and said second extension having a curved lip projecting downwardly from the arcuate pocket, said lips projecting a distance sufficient to prevent telescoping of said upper links during movement of said endless array of links along a curved path in a vertical plane.
 24. In a chain of the type having a section comprising three elongated links disposed in generally parallel superposed relation, means defining a slot in each link elongated along the length of the link and aligned with the slots in the other two links, and a pin extending through said slots connecting said links and having a transverse member at one end that is longer than said slots are wide, whereby said member is movable through said slots when disposed generally parallel thereto and is not movable therethrough when oriented transversely to said slots, the uppermost of said links having a recess on its upper surface extending transversely to the elongated slot in said uppermost link, the improvement which comprises a head on the other end of said pin opposite said one end of pin having said transverse member, said head having three equal projections spaced 90* apart, perpendicular to the longitudinal length of said pin and each projection having a length from the center of the pin approximately equal to the diameter of said pin, said head having a transverse portion formed by two of said three projections 180* apart overlying said transverse recess and said third projection overlying said longitudinal slot in said uppermost link, the upper surface of said head being substantially flush with the upper surface of said uppermost link to provide a substantially smooth continuous upper surface. 